1. Field of This Invention
This invention relates to a process for the production of aromatic trifluoromethyl compounds of the benzene series by conversion of the corresponding trichloro methyl compounds using hydrogen fluoride.
2. Prior Art
It is known, that compounds having one or more trichloromethyl groups on one aromatic nucleus can be converted with hydrogen fluoride in the presence of antimony methyl compounds into the corresponding trifluoro methyl compounds (see Houbeu-Weyl, "Methods of Organic Chemistry", vol. 5/3, pp. 124 and 125).
In U.S. Pat. No. 2,654,789 a process is described for the production of p-bis-(trifluorometyl) benzene (see col. 4, line 55 etc.). The trichloro compound is converted with an excess of hydrogen fluoride in the presence of antimony pentachloride, which is present in a quantity of about 1.0 percent related to the trichloro compound, at a temperature of 100.degree. C. and a pressure of about 34 atm. using a reaction time of around one hour into the corresponding trifluoro compound.
The known processes have the serious disadvantage of requiring large surpluses of hydrogen fluoride. For reasons of economy and of the protection of the environment, these surpluses must be recaptured, if possible, in order to feed them again into the reactor. Also, in order to carry out the reaction, relatively large quantities of antimony pentachloride are required as a catalyst. During the reaction the catalyst is decomposed, thereby becomes ineffective and must be continuously replaced.